Method for producing molded hose branches from rubber and a hose produced by the method

ABSTRACT

A method for producing molded hose branches of rubber and a molded hose branch produced according to the method, includes slipping completely vulcanized rubber hose lengths with ends onto free ends of a plastic tubing branching piece for forming an assembly, placing the assembly into a mold, and injection molding a thermoplastic rubber material in the form of a blended mixture of polypropylene and EPDM around the assembly for joining the thermoplastic material to the rubber hose lengths for forming a sleeve around the rubber hose lengths and free parts of the tubing branching piece between the ends of the rubber hose lengths.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation in part of application Ser. No.07/449,364 filed Dec. 4, 1989 which is a continuation-in-part ofapplication Ser. No. 07/206,267, filed Jun. 13, 1988 both now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a method for producing molded hose branchesfrom rubber, especially motor vehicle radiator or coolant hoses, inwhich fully vulcanized lengths of hose are slipped onto the free ends ofa plastic tubing branching piece and are secured in a fluid-tightmanner, as well as a molded hose branch produced according to themethod.

2. Description of the Related Art

A method of this kind is known from German Published, Non-ProsecutedApplication DE-OS 32 39 623. According to that method, suitable lengthsof hose are slipped onto a plastic or metal tubing branching piece whichhas flared free edge surfaces, with the introduction of a vulcanizableadhesive compound, and are completely vulcanized. As a result, evenalthough a firm coupling is produced and in particular freemanipulability of the location of the branch is attained, because of therepetitive stresses arising with radiator hoses especially due tofluctuating pressure in the interior of the hoses, there is the dangerthat the hoses, will come loose from the tubing branching piece, sincethere is no external clamping force that prevents the hoses fromstretching open.

It is accordingly an object of the invention to provide a method forproducing molded hose branches from rubber and a hose produced by themethod, which overcome the hereinafore-mentioned disadvantages of theheretofore-known methods and products of this general type and whichreliably intercept such repetitive forces so as to reliably avoidstretching open of the hoses in the vicinity of the coupling locationand a gradual loosening from the tubing branching piece.

SUMMARY OF THE INVENTION

With the foregoing and other objects in view there is provided, inaccordance with the invention, a method for producing molded hosebranches of rubber, which comprises slipping completely vulcanizedrubber hose lengths with ends onto free ends of a plastic tubingbranching piece for forming an assembly, placing the assembly into amold, and injection molding a thermoplastic rubber material being ablended mixture of polypropylene and EPDM(ethylene-propylene-diene-monomer) around the assembly for joining thethermoplastic material to the rubber hose lengths for forming a sleevearound the rubber hose lengths and free parts of the tubing branchingpiece between the ends of the rubber hose lengths.

The mixture of polypropylene and EPDM affords an integral and very firmbond between the sleeve and the rubber hose lengths. The sleeve and therubber hose lengths are virtually fused by the injection moldedthermoplastic composition.

In accordance with another mode of the invention, there is provided amethod which comprises joining the thermoplastic composition to thepolymer of the rubber of the rubber hose lengths in a molten state,forming a sleeve bonded to the rubber hose lengths.

In accordance with a further mode of the invention, there is provided amethod which comprises placing the tubing branching piece with therubber hose lengths slipped thereon in an injection mold defining aspace therebetween, and filling the space with the thermoplasticcomposition during the injection molding step.

Cross-spraying with such a material that bonds to the rubber hoses andhas a high modulus of elasticity, on the one hand assures a firm andfluid-tight coupling and retention of the hoses on the tubing branchingpiece and on the other hand reliably prevents the hoses from stretchingoutward and thus being able to come loose from the tubing branchingpiece over the course of time under load and operating conditions.

In accordance with an added mode of the invention, there is provided amethod which comprises selecting a polyolefin as the thermoplasticcomposition.

In accordance with an additional mode of the invention, there isprovided a method which comprises selecting polyethylene as thepolyolefin composition.

In accordance with yet another mode of the invention, there is provideda method which comprises selecting polypropylene as the polyolefincomposition.

With the objects of the invention in view, there is also provided amethod for producing molded hose branches of rubber, especially formotor vehicle radiator or coolant hoses, which comprises slippingcompletely vulcanized rubber hose lengths with ends onto free ends of aplastic tubing branching piece defining portions of the tubing branchingpiece covered by the rubber hose lengths and remaining portions,securing the rubber hose lengths to the free ends, injection molding theends of the rubber hose lengths slipped onto the tubing branching pieceand the remaining portions of the tubing branching piece with across-linkable composition having an affinity to a base polymer of therubber of the rubber hose lengths and having a modulus of elasticityhigher than that of the rubber of the rubber hose lengths by at leastone order of magnitude, and cross-linking the ends of the rubber hoselengths slipped onto the tubing branching piece and the remainingportions of the tubing branching piece with the cross-linkablecomposition under temperature.

In accordance with yet a further mode of the invention, there isprovided a method which comprises forming a sleeve bonded to the rubberhose lengths from the cross-linkable composition during the injectionmolding and cross-linking steps.

In accordance with yet an added mode of the invention, there is provideda method which comprises placing the tubing branching piece with therubber hose lengths slipped thereon in an injection mold defining aspace therebetween, and filling the space with the cross-linkablecomposition during the injection molding step.

In accordance with yet an additional mode of the invention, there isprovided a method which comprises selecting polyethylene with peroxideas the cross-linkable composition.

With the objects of the invention in view, there is furthermore provideda method for producing molded hose branches of rubber, especially formotor vehicle radiator or coolant hoses, which comprises slippingcompletely vulcanized rubber hose lengths with ends onto free ends of atubing branching piece formed of a cross-linkable composition having anaffinity to a base polymer of the rubber of the rubber hose lengths andhaving a modulus of elasticity higher than that of the rubber of therubber hose lengths by at least one order of magnitude, definingportions of the tubing branching piece covered by the rubber hoselengths and remaining portions, securing the rubber hose lengths to thefree ends, injection molding the ends of the rubber hose lengths slippedonto the tubing branching piece and the remaining portions of the tubingbranching piece with a layer of the cross-linkable composition, andcross-linking the ends of the rubber hose lengths slipped onto thetubing branching piece and the remaining portions of the tubingbranching piece with the layer of the cross-linkable composition undertemperature forming a sleeve bonded to the rubber hose lengths.

It is particularly suitable for the same material to be used for thetubing branching piece as for the sleeve, because in that case thetemperature action also brings about bonding of the rubber hoses to thetubing branching piece.

In accordance With still another mode of the invention, there isprovided a method which comprises selecting EPDM rubber as the materialfor the rubber hose lengths.

In accordance with still a further mode of the invention, there isprovided a method which comprises locking the tubing branching piece tothe slipped-on rubber hose lengths with an encompassing, substantiallysawtooth-shaped rib on the free tube ends of the tubing branching piece.

In accordance with still an added mode of the invention, there isprovided a method which comprises vulcanizing hose end pieces having thesame shape as the free ends of the tubing branching piece onto therubber hose lengths prior to slipping the rubber hose lengths onto thefree ends of the tubing branching piece. This is done in order toimprove the form-locking effect. A form-locking connection is one whichconnects two elements together due to the shape of the elementsthemselves, as opposed to a force-locking connection, which locks theelements together by force external to the elements.

With the objects of the invention in view, there is additionallyprovided a molded hose branch, especially for motor vehicle radiator orcoolant hoses, comprising a rigid plastic tubing branching piece havingfree ends, rubber hose lengths slipped and secured onto the free ends ofthe tubing branching piece defining portions of the tubing branchingpiece between the rubber hose lengths, and a sprayed-on compositionsurrounding and joining the rubber hose lengths and the portions of thetubing branching piece, the composition being bonded at least to therubber hose lengths and having a modulus of elasticity higher than thatof the rubber of the rubber hose lengths by at least one order ofmagnitude.

In accordance with another feature of the invention, the compositionforms a sleeve with a modulus of elasticity of substantially between 500and 3000 N/mm².

In accordance with a further feature of the invention, the free tubeends of the tubing branching piece have outer surfaces with encompassingribs formed thereon form-locking the slipped-on rubber hose lengths tothe tubing branching piece, the ribs having substantiallysawtooth-shaped cross sections and sides dropping off gently toward thefree tube ends.

In accordance with an added feature of the invention, the tubingbranching piece has an outer surface with radially protruding pin-shapedstops formed thereon in the vicinity of the free ends of the tubingbranching piece for stopping the rubber hose lengths.

In accordance with a concomitant feature of the invention, the rubberhose lengths have end pieces vulcanized thereon, the end pieces havinginner contours corresponding to the sawtooth-shaped ribs.

Other features which are considered as characteristic for the inventionare set forth in the appended claims.

Although the invention is illustrated and described herein as embodiedin a method for producing molded hose branches from rubber and a hoseproduced by the method, it is nevertheless not intended to be limited tothe details shown, since various modifications and structural changesmay be made therein without departing from the spirit of the inventionand within the scope and range of equivalents of the claims.

The construction and method of operation of the invention, however,together with additional objects and advantages thereof will be bestunderstood from the following description of specific embodiments whenread in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fragmentary, diagrammatic, cross-sectional view of a tubingbranching piece, such as in the form of a T, having lengths of hoseslipped onto it, in a prefabricated state;

FIG. 2 is a view similar to FIG. 1 of a finished hose branch with asprayed-on sleeve; and

FIG. 3 is a fragmentary, cross-sectional view of an end of a hose havinga separately vulcanized-on end piece.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the figures of the drawings in detail and first,particularly, to FIGS. 1 and 2 thereof, there is seen a simplifiedembodiment of a hose for a branch having a single T-shaped hose branch,since the principle of the invention can be explained most simply withthis embodiment. As can be seen from FIG. 1, a T-shaped branch 1 isprimarily formed of a T-shaped tubing branching piece 2 having freetubing stubs or ends 3, 4 and 5. The stub 5 forms the actual branchwhich is attached at an angle of 90°. However, the actual branch mayalso be attached to the main tube at any other arbitrary angle dependingon the required application for the branch. Moreover, it is equallypossible to place a plurality of branches and not merely one branch atvarious three-dimensional or solid angles relative one another. Thetubing branching piece 2 is to be firmly joined to individual lengths ofhose 6, 7 and 8 that form the finished branch or branching piece 1.

In order to provide a mechanical, form-locking coupling, the outsides ofthe free tube ends or tubing stubs 3, 4 and 5 of the tubing branchingpiece 2 each have an encompassing rib 10 with an approximatelysawtooth-like cross section and a side 11 gradually dropping off towardthe tube end. A form-locking connection is one which connects twoelements together due to the shape of the elements themselves, asopposed to a force-locking connection, which locks the elements togetherby force external to the elements. The pieces of hose 6, 7 and 8 cantherefore be easily slipped over these ribs 10, while a retraction iscounteracted by considerable resistance because of the sawtooth-likestructure of the ribs.

In order to accurately position the lengths of hose 6, 7 and 8 on theT-shaped piece in the radial direction as well, the outside of thetubing branching piece 2 may also be provided with radially protrudingpin-like stops 12, which limit the extent to which the correspondinglengths of hose 6, 7 and 8 may be slipped on.

The hose branch which has been prefabricated in this way is then placedin a non-illustrated mold and, in accordance with FIG. 2, it isinjection molded with a material forming a sleeve 15 that covers thehose ends 6, 7 and 8 and the free regions or remaining portions of thetubing branching piece 2 between the hose lengths in the space betweenthe mold and these parts. The material then sets or cross-links.

The material used for the sleeve 15 should be a thermoplastic orcross-linkable composition that has a modulus of elasticity which isvery much higher than that of the rubber, in other words at least oneorder of magnitude greater. A polyolefin such as polyethylene orpolypropylene is particularly suitable as the thermoplastic composition.A polyethylene with peroxide can be used as the cross-linkablecomposition. In the preferred embodiment and the best mode, the materialforming the sleeve 15 is a thermoplastic material which is a blendedmixture of polypropylene and EPDM.

An essential factor in this case is that the curable or cross-linkablecomposition has an affinity for, or is chemically identical to, a basepolymer of the rubber. EPDM is preferably used as the rubber for thehose lengths. In fact, besides the cross-linked portion, an EPDM of thiskind has sufficiently long chain-like segments that can be melted on, sothat at a suitable temperature of the sleeve material, a bonding of thesleeve 15 to the hose lengths 6, 7 and 8 takes place and thus afluid-tight, firm coupling between the sleeve 15 and the lengths of hose6, 7 and 8 which cannot be undone by mechanical strains, is assured.

If the tubing branching piece 2 is additionally made from the samematerial as the sleeve 15, then not only does bonding take place betweenthe branching piece 2 and the sleeve 15 but also between the tube ends3, 4 and 5 and the slipped-on hose lengths 6, 7 and 8. Thus theselengths of hose 6, 7 and 8 are not only bonded to the sleeve 15 towardthe outside but are also bonded to the branching piece 2 toward theinside and are thus firmly joined with them, so that stretching of thehose lengths 6, 7 and 8 and resultant detachment from the branchingpiece 2, is practically no longer possible.

This stretching of the hose lengths 6, 7 and 8 is also prevented byproviding that the sleeve 15 has a modulus of elasticity that is higherby at least one order of magnitude than that of the rubber. Suitably,the modulus of elasticity of the sleeve 15 should be on the order ofmagnitude of approximately 500 to 3000 N/mm² at room temperature.

Since the longitudinal extension of the sleeve 15 also extends over thevicinity of the form-locking couplings provided by means of the ribs 10and thus forms a rigid binding in this region, additional securityagainst detachment of the hose lengths 6, 7 and 8 is provided.

In order to assure that the hose ends rest tightly in the vicinitybetween the ribs 10 and the stops 12, it is advantageous for the hoselengths 6, 7 and 8 to have separately vulcanized-on end pieces 20 asshown in FIG. 3. The inner contour of the end pieces 20 corresponds tothe outer contour of the branching piece 2 in the vicinity of the ribs10 Due to the likewise sawtooth-like groove 21 thus formed in thevulcanized-on end pieces 20, a direct form lock with the correspondingouter contour of the tubing branching piece 2 is produced when the hoselengths are slipped on.

With the method described above, it is thus possible in a simple mannerto provide a hose branch which has any arbitrary configuration as wellas a variable number of hose branches, which are simple to manufactureand are extremely durable even when subjected to repetitive stresses atelevated temperature.

We claim:
 1. Method for producing flexible molded hose branches ofrubber, which comprises slipping three completely vulcanized rubber hoselengths with ends onto free ends of a T-shaped plastic tubing branchingpiece for forming an assembly, placing the assembly into a mold, andinjection molding a thermoplastic rubber material being a blendedmixture of polypropylene and EPDM around the assembly for joining thethermoplastic material to the rubber hose lengths for forming a sleevearound the rubber hose lengths and free parts of the tubing branchingpiece between the ends of the rubber hose lengths.
 2. Method accordingto claim 1, which comprises selecting EPDM rubber as the material forthe rubber hose lengths.
 3. Method according to claim 1, which compriseslocking the tubing branching piece to the slipped-on rubber hose lengthswith an encompassing, substantially sawtooth-shaped rib on the free tubeends of the tubing branching piece.
 4. Method according to claim 3,which comprises vulcanizing hose end pieces having the same shape as thefree ends of the tubing branching piece onto the rubber hose lengthsprior to slipping the rubber hose lengths onto the free ends of thetubing branching piece.